Issue #12931 has been updated by Nobuyoshi Nakada.
Status changed from Open to Rejected
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Feature #12931: Add support for Binding#instance_eval
https://bugs.ruby-lang.org/issues/12931#change-62559
* Author: Samuel Williams
* Status: Rejected
* Priority: Normal
* Assignee:
* Target version:
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Many people would probably like to use `binding.instance_eval` when executing templates. The reason for this is because `binding.eval` is slow.
The use case is template rendering, e.g. systems like ERB.
In my template renderer, I did have
```ruby
if Binding === scope
# Slow code path, evaluate the code string in the given binding (scope).
scope.eval(code, @buffer.path)
else
# Faster code path, use instance_eval on a compiled Proc.
scope.instance_eval(&to_proc)
end
```
The binding path is several orders of magnitude slower because the code is a string and must be parsed, compiled, etc. But, `to_proc` path can be cached.
In terms of duck typing, it would be nice if binding implemented `#instance_eval` and would allow passing a block.
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